In many industrial applications involving the use of water, it is essential that the salinity concentration of impurities within that water system be under constant surveillance to provide instant alarming in the event that predetermined concentration limits are reached or exceeded. An example of a particular application in which salinity monitoring is essential is in fluid lines carrying water for use in ship systems where high salinity impurity of the water is potentially dangerous and destructive. Usually, such salinity monitoring systems are installed at unmanned locations and are monitored at remote locations by means of meters, indicators, warning lights and alarms.
In shipboard monitoring systems, it is essential that impurities of a very low order be immediately detected and signaled so that remedial steps can be initiated to avoid substantially damage to the system equipment. It is desirable, therefore, that the monitoring equipment provide effective, dependable and precise continuous sampling at all test locations at which impure concentrations may develop and to provide arrangements for attracting the attention of operating personnel to initiate remedial steps without delay. Additionally, the system should provide for constant indication of salinity concentration and for operating alarms in the event that predetermined levels of concentration impurities are reached or exceeded. The monitoring equipment should also provide for automatic dumping of the contaminated water without the delay necessarily involved when personnel must intervene. Some methods and systems have been suggested for providing surveillance of this type; however, these prior art systems have proved to be inadequate because of the very low order concentrations of impurities which must be detected in view of the variable factors for which such systems must compensate in order to provide the needed degree of precision.
It is generally recognized that as the concentration of salinity decreases, the resistive response of water to temperature changes increases. Tests data indicate an increase of water sensitivity in the order of thirty percent as between pure water and ultra-pure water. Thus, one fixed temperature compensation technique will not compensate for the various ranges of salinity encountered. Since a one-thermistor and one-resistive network will not produce optimum performance except for one purity of water, the temperature compensation technique must be adapted for each purity of water encountered in order to produce high precision compensation. The typical prior art method of handling this temperature compensation problem has been to shape the compensating thermistor with a resistive network located in the electronic panel and to switch between the various compensating networks as different water purity ranges are encountered. In the present invention the special shaping resister network and thermistor are mounted inside the cell and function both as to shape the response for the water and for scaling the electronics.
Some prior art salinity monitors function for the dual purpose of providing a trigger alarm to indicate an impure water condition and also to cause dumping of the impure water. These prior art salinity monitors have provided control panels having these two set points the same or related in some manner. It would be helpful to have a salinity monitoring system having independent set level controls for the alarm function and for the dump function. By having early warning of a pending out of limits water condition, it would be possible to adjust plant operation to correct the problem without having to actually dump and waste water. Also, it would allow operating personnel to schedule corrective action at a convenient time. Therefore, it would be an improvement over the prior art to have a salinity monitoring system having a dump trigger level set at a specified water limit and an alarm level set at a somewhat more sensitive level so as to cause the system to alarm to indicate a pending out of limits condition prior to the time the dump action is triggered.
Typical prior art salinity monitoring systems usually provide one alarm lamp per engine room console and that single alarm lamp signals only abnormal salinity conditions to the exclusion of other alarm conditions such as low temperature, insufficient pressure on various pumps, purging cycle and process and out of limits pH. The prior art salinity monitors have no summary alarm means for signaling alarm conditions involving these other perimeters. It would be helpful to have all alarm conditions signaled through a signal relay, an alarm relay.
Typical prior art salinity monitoring systems have the panel remotely located from the engineer watch station so that the alarm signal must be electrically transmitted to the engineer via the console flashing alarm. A high salinity condition on any of several channels causes the console to go into an alarm situation and the engineer acknowledges the situation by controls at the engineering console. In the typical prior art salinity panel, a subsequent salinity alarm occuring on any of the other channels would not cause the engineering console to realarm if the first alarm situation had not been cleared. While the salinity monitor would indicate this new alarm situation locally, it would not signal such subsequent alarm situation at the watch station. It would be helpful in salinity monitoring systems to provide not only high salinity situations, but also dumping conditions, low pressure and below normal temperatures at the console.
Typical prior art salinity monitoring systems, particularly those involved in marine application, provide for an alarm acknowledge function whereby a watchstander notes an alarm condition, identifies the cause and acknowledges the alarm condition. When the alarm condition is acknowledged, the audible alarm is silenced and the alarm indicator lamp goes from blinking to steady-on in preparation for receiving another alarm condition. In marine salinity monitors which are required to sense not only salinity, but also pH, low temperature, purge cycle, dumping and low pressure, a technique of alarm acknowledgement is needed.